1. Field of the Invention
The present invention relates to video transmission/reception systems. More specifically, the present invention relates to a protocol and apparatus for transmitting information in conjunction with a video signal.
2. Background Information
With the proliferation of personal computer systems and the decline in costs of high-capacity computer technology in general, the technologies of television transmission and computer applications are starting to merge. Solutions have been slow in coming, however.
For certain applications in television program transmission, it is desirable to transmit information in addition to the audio/video portion of the signal. For example, closed-captioned programming is now being used extensively to serve the needs of the hearing-impaired. In fact, recent requirement for television receivers include the requirement that all receivers provide this capability to display, in text, the audio portion of the transmitted program.
For news programming, other needs have arisen. For example, for 24-hour a day news programming, real-time stock quotes and sports scores are now being displayed as part of the video portion of the signal on services such as Headline News (a trademark of Turner Broadcasting, Inc.). Although this serves the needs of the viewer, providing such real-time information, this solution not only distracts the viewer of the video screen, but also unnecessarily consumes screen space, and does not allow the viewer to view the information which is of interest to him. For example, to view the price of a particular stock, the viewer has to wait until the ticker cycles back to display that information. The same deficiency is true for sports scores. Other viewers, such as those requiring real-time weather information needs are also not met. Thus, an improved means for obtaining such information is required.
Prior art solutions such as closed-captioning use the vertical blanking interval (VBI) for encoding text for the audio portion of the programming. It typically uses line 21 of the vertical synchronization portion of the video signal. Thus, although it does not interfere with the transmission of the video signal, it has lacked the capability to be used in any other way, rather than real-time display to the viewer, such as for indexing of the television program, full-text capture of information conveyed by the program, and/or other text processing operations commonly performed in modern personal computer word processing application programs.
Another shortcoming of closed-captioning is that although it uses a portion of the VBI for transmission (line 21), is does not make efficient use of the bandwidth of that portion of the non-displayed video signal. It is estimated that a single line of the VBI can be used for uncompressed data transmission at approximately 14.4 kilobytes/second. Thus, real-time closed captioning of the audio program of a televised broadcast does not take full advantage of the bandwidth of the signal. It also is a unichannel system, wherein only the closed captioning information is transmitted, rather than taking advantage of the full-bandwidth of the signal.
Prior art information which has been transmitted in conjunction with television programming sometimes only transmits limited information about the programming. For example, in consumer satellite television reception systems, usually only text information describing the title of the program, and at most, the time elapsed or time remaining in the program has been transmitted with the programming. More detailed information, such as references to outside sources related to the programming, or other information, which is synchronized with the programming has not been transmitted in conjunction with the signal.
Thus, the prior art for transmitting information with television programming suffers from several shortcomings.